1. Technical Field of the Invention
The invention relates to a countersunk head screw with a head, with a shank, and with a thread extending at least partially over the shank, whereby the head, at least in sections, features a bearing surface that tapers conically toward the shank.
2. Discussion
Screws of this kind are known. For example, they may feature a drive groove, such as a slot or a cross recession for engaging the screwdriver. The open end of the shank can be shaped as a point. In particular, we can be dealing with countersunk head screws that have the effect of shaping or cutting a thread into the material into which they are screwed.
When mechanized screw drivers are used, a problem appears in that the screws, short screws such as fitting screws above all, will spin after they have been completely or almost completely screwed in, i.e. they rotate in place without penetrating deeper into the material. This can destroy threads that have been shaped or cut into the material.
It is the objective of the invention, to improve a countersunk head screw of the type described in the introduction, so that the negative occurrences cited above can be prevented.
In accordance with the teachings of the present invention, a countersunk head screw is provided. The countersunk head screw includes a head connected or integrally formed with a shank. A thread extends at least partially over the shank and a section of the head includes a bearing surface that tapers conically towards the shank. At least one restraint rib is arranged in a top region of the bearing surface turned away or spaced apart from the shank. Additionally, at least one cutting rib is arranged in a lower region of the bearing surface that is facing or adjacent the shank.
The objective of the invention is achieved by arranging restraint ribs in a top region of the bearing surface turned away, or spaced apart, from the shank.
When a screw in accordance with the invention is being screwed in, these restraint ribs cause increased compression of the surface between the screw and the material that it""s being screwed into, a fitting""s metallic surface for example. This increases the frictional resistance and counteracts the screwdriver""s moment of rotation, whereby spinning of the screw can be efficiently prevented.